Scanning charged particle microscopes which have a detector system for detecting cathodoluminescence light are commonly known. Cathodoluminescence provides an especially powerful analysis tool in the study of semiconductors. The energy levels in semiconductor materials and insulators are affected by the concentrations of impurities, carriers and electrically active defects. Also in geology, mineralogy and biology, cathodoluminescence has a wide range of applications.
Cathodoluminescence light is generated when the beam of charged particles impinges on the object surface, thereby causing a variety of excitations that result in radiation emitted from the interaction volume of the electron beam with the sample. The radiation may be in the visible range, ultraviolet range and/or in the infrared range.
The emitted light is analyzed to generate spectrally resolved cathodoluminescence images of the sample or local cathodoluminescence spectra. These data are indicative of the material composition of the object and of the chemical state of the present elements. Also, information with regard to mechanically induced defects in crystals, as well as processes, such as crystal growth, replacement, deformation and provenance can be derived from cathodoluminescence data.
For efficiently investigating the object's material composition, it is desirable for the cathodoluminescence light collection system to provide high light collection efficiency. This can allow detection even small fractions of materials within the object. Furthermore, cathodoluminescence light emission is often inherently low from specimens which are often used in geology and life sciences. For detector systems having low light collection efficiency, this may lead to long acquisition times.
Light collection systems which are optimized with respect to light collection efficiency can be difficult to arrange close to the interaction volume of the particle beam with the object because the objective lens, particle detectors and instrumentation for sample preparation and navigation usually take up considerable installation space.